#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

 //* Definition for singly-linked list.
  struct ListNode {
      int val;
      struct ListNode *next;
  };
 


struct ListNode* mergeTwoLists(struct ListNode* l1, struct ListNode* l2) {
    struct ListNode* head = NULL, * tail = NULL;
    if (l1 == NULL)
        return l2;
    if (l2 == NULL)
        return l1;
    if (l1->val < l2->val)
    {
        head = tail = l1;
        l1 = l1->next;
    }
    else
    {
        head = tail = l2;
        l2 = l2->next;
    }
    while (l1 && l2)
    {
        if (l1->val < l2->val)
        {
            tail->next = l1;
            tail = tail->next;
            l1 = l1->next;

        }
        else
        {
            tail->next = l2;
            tail = tail->next;
            l2 = l2->next;

        }
    }

    if (l1)
        tail->next = l1;
    if (l2)
        tail->next = l2;
    return head;
}
int main()
{
    return 0;
}